"We have guys diving, and I don't have to make that many saves," the Atlanta goaltender said. "I think we dominated almost the whole game, so that's a good sign."
Marc Savard also scored on a first-period penalty shot for Atlanta, which snapped a two-game losing streak. The Thrashers are ninth in the Eastern Conference with 78 points, five behind Tampa Bay for the eighth and final playoff spot.
Carolina, which won the Southeast Division after ending Florida's seven-game winning streak on Friday, has lost five of nine.
"It was a must-win tonight, and it was great to get those two points," Lehtonen said. "We need to just keep going like that."
The Thrashers have almost no room for error. With 78 points, they are five behind Tampa Bay and seven back of Montreal and New Jersey. Florida, which beat the Lightning 4-2 Saturday, has 77 points -- one more than Toronto.
"It's tough, because if you lose, you obviously lose ground, and if you win, you stay there," Atlanta coach Bob Hartley said. "We just have to keep winning games and hope teams start getting in trouble."
Kovalchuk's 46th goal, at 4:03 of the second, made it 3-0. As Scott Mellanby lost control in a left-circle battle with Craig Adams and Oleg Tverdosky, Kovalchuk picked up the puck as he raced through the top of slot and used a snap shot to beat goaltender Cam Ward.
"The game plan was clear -- don't turn the puck over, get it deep and establish the grind," Hurricanes coach Peter Laviolette said. "We wanted to think we were better than them, and we turned the puck over."
Carolina cut the lead to 3-1 at the 12:34 mark of the second on Matt Cullen's slap shot from top of the slot.
Kovalchuk answered Cullen's goal 56 seconds later. Taking Brad Larsen's pass from the neutral zone, Kovalchuk put the Thrashers ahead 4-1 by beating Ward with a wrister from the right circle.
"The most important thing was to win the game," Kovalchuk said. "We have to play our best hockey and play every game like it is the last game."
Cullen had an assist when Rod Brind'Amour beat Lehtonen for a short-handed goal in the final minute of the period to close out the scoring.
"They capitalize on opportunities as good as anyone in the league," Cullen said of Atlanta. "You can't give them any space, and if you do, you're going to pay."
Savard, who had two goals in his last 17 games, earned a penalty shot after Ward extended his stick and knocked him down. Savard lifted the puck over Ward's left shoulder for his 27th goal 11:39 into the game.
Jim Slater's eighth goal made it 2-0 at the 13:51 mark of the first.
Ward, who gave up five goals in a 5-1 loss to Washington on Wednesday, stopped 13 of 18 shots to fall to 13-8-2.
Lehtonen made 35 saves to improve to 19-14-0.
The first period also included a game misconduct and ejection for Carolina's Mike Commodore.
- Savard became the first Thrasher to score a penalty shot in Atlanta.
- The Thrashers improved to 3-7-6 against Carolina at Philips Arena.
- Cullen now has 100 career goals.
- Carolina went 0-for-6 to fall to 5-for-52 on the power play in its last eight games.
- With 89 points, Savard now has one more than Dany Heatley recorded for a single-season franchise record in 2002-03.
- Kovalchuk now has 88 points this season and eight goals in seven games against the Hurricanes.